1. Field of the Invention
The present invention pertains to a machine that dispenses objects and detects the dispensed objects with an optical sensor, and more particularly to an optical vend-sensing system and a vending machine that has an optical vend-sensing system.
2. Description of Related Art
In a typical glass-front vending machine, the user of the machine sees a glass-fronted cabinet, with a selector panel located off to one side of the glass. Through the glass, there can be seen an array of articles, typically packaged snack foods arranged in horizontal columns which extend horizontally in a front-to-rear depthwise direction, with a plurality of columns at each of several vertically spaced levels. At each level the articles are pocketed in-between adjacent turns of respective spirals arranged one or two to a column. Each spiral has an axially central rearwardly projecting stem at its rear, which is plugged into the chuck of a respective motor assembly mounted to the rear of a tray. When a user makes the requisite payment to the machine and makes a desired selection on the selector panel, the spiral or spirals for the respective column begin to turn causing all of the packaged articles received among the spiral turns in that column to advance. If the vending machine is working properly, the respective spiral or spirals turn sufficiently to cause the leading packaged article in the respective column to be conveyed sufficiently far forwards that the package loses support provided from underneath by a respective tray, and tumbles down past the front of the respective shelf, through a vend space between the fronts of the columns and the back of the glass front, into an outlet bin, from which the user can retrieve it, typically by temporarily pushing in a hinged from above, normally closed door. Again, if the machine is working properly, the respective spiral or spirals cease being turned by the respective motor assembly before the next-in-line, newly leading package in the respective column mistakenly becomes conveyed so far forwards that it, too, falls off the tray, down through the vend space and becomes vended without a requisite payment having been made.
Several different unplanned occurrences can occur, and the possibility and likelihood of their occurrence complicates the design of glass-front vending machines.
It is important that users, upon making requisite payment, be reliably vended the product which they have selected, without any deficiency or bonus, and without any need, or apparent desirability for expending unusual effort, or that the user automatically be provided a return of payment, or the opportunity to make another selection.
Spatial orientation of packages and wrinkling of packaging, unusual distribution of contents of a package, unusual tumbling of a package through the vend space, an empty pocket in a spiral and similar factors all can cause mis-vending, particularly if the machine is one in which a spiral is made to turn through only a predetermined angular distance for vending a selected product, or the package being vended, depending on how it falls, can bypass a detector meant to terminate rotation of the respective spiral or spirals upon detecting that a package has been vended.
Many glass-front vendors are modularly constructed, so that the number of vertically-spaced rows of product columns, and/or the number of laterally spaced columns per row can be changed either at the time the machine is ordered by its purchaser, or in the field, or both. This fact also complicates provision of reliable vending, particularly if adding and deleting columns necessitates adding and deleting sensors and making sure that the sensors are properly positioned and correctly operating. Addition of sensors also adds to expense.
It is known in the art to provide an emitter and detector which provide a beam in a confined space through which the vended product will fall. However, there is some chance that the falling product, through happenstantial orientation will fail to break the beam, or will apparently fail to break the beam, and therefore not be detected. There is also a possibility that in constricting the space through which the product must fall, happenstantial orientation will cause the product to bridge and become lodged in the constricted space, having been detected but not having been successfully vended.
Others have provided vend sensors in which the impact on the outlet chute of a comparatively heavy vended article such as a can or bottle, is sensed as a vibration. However, such sensing is not economically feasible where at least some of the products being vended are very light in weight, such as is the case where a small number of large potato chips are presented in a facially large but light in weight package made of synthetic plastic film.
A particularly difficult situation is presented when some of the products to be dispensed are large so that a large transverse cross-sectional area is required for the vend space, but others of the products are so small that an optical beam meant to be broken by the product could be missed due to happenstantial path of movement and changing spatial orientation of the falling product being vended.
Some terminology used in this document is used in an exemplary way which is not intended to limit the applicability of the broader concepts of the invention. For instance, the terms article, packaged product, product and the like are not intended to limit the concept of what object can be vended, or otherwise dispensed. Use of the term glass is not intended to mean that the front of the vendor cannot in whole or in part be made of another material.
Although the manufacturing costs may be lower, there can be more risk of faulty operation if a rotary spiral-type vending machine is designed simply to have the respective spiral or spirals turn through a prescribed number of degrees and/or for a prescribed amount of time before ceasing to turn, i.e. without any vend sensor. The customer who sees the machine quit operating but not having received a product, which may be noticeably close to being vended, may rock the machine thinking to provide enough physical encouragement as to accomplish the vending of the product, but result in damaging the machine and perhaps injuring themselves.
And, to the extent that the cost of providing a xe2x80x98homexe2x80x99 switch for terminating motor operation after each respective spiral has turned through the angular distance calculated to be sufficient to vend a product adds to the cost of the machine, vending control based on extent of rotation limitation may not be less expensive than vend sensing.
Accordingly, it is an object of this invention to provide an optical vend-sensing system which detects an object that has actually been vended.
It is another object of this invention to provide an optical vend-sensing system which detects vended objects which are of various sizes and shapes.
It is another object of this invention to provide an optical vend-sensing system which is robust against background noise and stray signals and against intentional attempts to disrupt the detection system.
It is yet another object of this invention to provide a vending machine which has an optical vend-sensing system as indicated above.
It is another object of this invention to provide a method of detecting a dispensed object with an optical sensor which can detect dispensed objects of various sizes and shapes.
It is another object of this invention to provide a method of detecting a dispensed object such that it is robust against background noise, interference signals, and intentional attempts to disrupt the operation of the system.
For ensuring that a vending machine motor will continue to operate until a product has descended through a vending space or an established time interval has elapsed, a continuous optical beam is established across the vend space through which a product must drop. Preferably, the beam is thin for good sensitivity, but not so thin that it leads to alignment problems. A change in beam intensity is detected. In a first embodiment, infra-red light is emitted by a row of emitters, spread into a beam by a diffuser, and detected by a segmented detector arrangement, including two side by side curved, mirrored-surface collectors. The collectors have a reflecting surface that is a section of a parabola that focuses the collected light onto a photodiode disposed substantially at the focal point of the parabolic surface.
In a second embodiment of the invention, the collector is a heel-shaped component which has a first reflecting surface that is substantially flat. The flat reflecting surface of the collector in the second embodiment of the invention reflects the incoming light in the direction of the edge of the heel-shaped collector. The heel-shaped collector has an edge that is substantially parabolic and is a second reflecting surface. Light reflected from the parabolic edge of the heel-shaped collector is reflected to a photodiode or a dimple reflector constructed and arranged substantially at the focal point of the parabolic edge of the heel-shaped collector. The surface of the dimple reflector is preferably substantially an inverted parabolic shape such that the light incident on the dimple reflector is redirected as a substantially collimated beam directed substantially normally to the heel-shaped collector, substantially at the focal point of the parabolic edge of the heel-shaped reflector. An electromagnetic radiation detecting element, such as a photodiode, is disposed in the path of the collimated beam formed by the dimple reflector.
In a third embodiment of the invention, a substantially elliptical reflector has an inner reflecting surface which is formed like an elliptical belt. In the preferred embodiment, a single emitter is disposed substantially at a first focal point of the elliptical reflector. More preferably, a dimple reflector is disposed substantially at the first focal point of the elliptical reflector such that light provided by the emitter in a direction orthogonal to the plane of the elliptical reflector is redirected towards the reflecting surface of the elliptical reflector, substantially in the plane of the elliptical reflector.
An electromagnetic radiation detecting element is disposed at the second focal point of the elliptical reflector in the second embodiment of the invention. More preferably, a second dimple reflector is provided at the second focal point of the elliptical reflector and a photodiode is disposed proximate to the dimple reflector such that light reflected by the elliptical reflector and converged onto the dimple reflector at the second focal point of the elliptical reflector is redirected substantially in a collimated beam orthogonal to the plane of the elliptical reflector. This provides a band of electrical magnetic radiation, preferably infra-red light, within an interior region defined by the elliptical reflector. An object to be detected, such as a vended item, passes through the beam of light provided within the interior region defined by the elliptical reflector.
In each of the three currently preferred embodiments, the photodiode provides an output signal which is processed to determine whether an object has passed through the beam of preferably infra-red light. In general, the band of electromagnetic radiation can be provided in either a continuous wave or a pulsed mode. In the preferred embodiments, the electromagnetic radiation is pulsed infra-red radiation.